Biodegradation kinetics and fate modelling of pentachlorophenol in bioaugmented activated sludge reactors

The growth and biodegradation kinetics of Mycobacterium chlorophenolicus comb nov. was studied in a series of batch experiments in the laboratory to identify and quantify the significant factors for its bioreactor performance. A mathematical model was formulated taking into account the degradation of primary and secondary substrate, as well as the growth of nonspecific and specific biomass. Using model parameters determined by the batch tests, the model was validated by simulations of a continuous flow experiment with bioaugmentation of the PCP-degrading culture in 2 activated sludge systems. A novel technique using immunofluorescence microscopy for quantifying the pure culture made it possible to evaluate the specific PCP degradation rates related to the PCP-degrading culture. The comparisons showed an excellent agreement for the total PCP removal, although there were some over- and underestimations of sorption and biodegradation as individual removal processes. The specific first order biodegradation rate constants were about 3 times higher in the bioaugmented systems that in batch experiments with the added culture alone. Even rough estimates for specific biodegradation rate constants may give meaningful predictions of the fate of specific organic compounds in wastewater treatment processes. For practical engineering and management purposes this may in many cases be adequate. The study highlighted the importance of reporting operating conditions in experiments from which biodegradation kinetic parameters such as Y, μm and KS were derived.